The Effect of Different Chemical and Physical Treatments on Seed Coat Structure and Seed Germination of Sesbania Species

Abstract

Summary Seed coats of Sesbania bispinosa and Sesbania punicea were rendered permeable by acid scarification treatments of 30 and 90 minutes respectively. Dry heat treatments increased seed coat permeability in both species. Long exposure times and/or higher temperatures were most effective in bringing about loss of seed coat impermeability and seed viability. Wet heat treatments which required shorter exposure times and lower temperatures, were more effective than dry heat treatments in softening the seed coats of the two species. Alternate freezing and thawing had only a very marginal effect on seed coat permeability in either species. Immersion in 100% acetone had little or no effect on the seed coats of S. punicea but after 42 days immersion the seed coats of S. bispinosa had been rendered permeable. Immersion in 75% acetone had no effect on either species. Dry heat, wet heat, acid scarification, mechanical scarification and immersion in acetone all resulted in structural changes in the macrosclereid layer of the seed coat of both Sesbania species. These changes could in most cases be related to loss of seed coat impermeability. Results indicate that the barrier to water movement extends to some depth into the macrosclereid layer. Seed moisture content can be related to seed coat impermeability in S. punicea but not necessarily in S. bispinosa .